The present invention generally relates to the field of reciprocating saws.
Reciprocating saws are used to cut a variety of objects, such as metal pipes, wood and drywall. Such saws typically include a housing and a spindle mounted in the housing for reciprocating motion along an axis that is parallel to the longitudinal extent of the spindle. An electric motor provides power to the spindle through a mechanical reciprocating device that converts the rotary motion of a motor shaft to reciprocating motion. Such mechanical reciprocating devices can, for example, include an eccentric drive, as disclosed in U.S. Pat. No. 5,079,844, or a wobble plate drive, as disclosed in U.S. Pat. Nos. 5,025,562 and 5,050,307.
In some reciprocating saws, the spindle reciprocates in an orbital motion as opposed to a straight line reciprocating motion. The orbital motion is characterized by a forward (i.e., in the cutting direction) motion of the saw blade as the saw blade is being retracted toward the saw on the cutting stroke, and a corresponding rearward (i.e., opposite the cutting direction) motion of the saw blade as the saw blade is being extended away from the saw on the return stroke. The result is a circuitous, or orbital, path of the saw blade. Such orbital motion is believed to improve the speed at which the saw cuts a workpiece by driving the saw blade into the workpiece during the cutting stroke and withdrawing the saw blade from the workpiece during the return stroke.
Orbital motion has been achieved in a number of different ways. For example, in U.S. Pat. Nos. 4,238,884 and 4,628,605, a forward force (in the cutting direction) is applied by a blade roller directly to the saw blade during the cutting stroke, and forward motion of the saw blade is accommodated by a forgiving interconnection between the spindle and the drive mechanism. In U.S. Pat. No. 5,212,887, the spindle reciprocates through a pivotally-mounted bushing, and the back end of the spindle is connected to an eccentric member that provides forward-rearward motion to the spindle. In U.S. Pat. Nos. 4,962,588 and 4,550,501, the back end of the spindle is moved forward-rearward by connection to a cam surface on a rotating gear, and in U.S. Pat. No. 5,392,519 the back end of the spindle in moved forward-rearward by connection to an eccentric member.
The utilization of blade rollers, cam surfaces, and eccentric members can be unnecessarily complicated and expensive. Further, such devices tend to wear down, and some can introduce unwanted vibrations into the saw. Accordingly, it is an object of the present invention to provide a saw that approaches the better cutting performance of orbital saws without the complexity required for orbital motion. It is a related object of the present invention to achieve a forward motion of the saw blade during the cutting stroke without resorting to orbital motion.
The above-noted objects are achieved by a method of reciprocating a spindle of a reciprocating saw, the spindle having a front end adapted to receive a saw blade movable through a cutting stroke and a return stroke. The method comprises the steps of reciprocating the front end along a first path (e.g., a neutral path) during the cutting stroke and along the same first path during the return stroke, and adjusting the saw such that the front end reciprocates along a second path during the cutting stroke and along the same second path during the return stroke. The second path is oblique to the first path. By virtue of this method, the front end of the spindle follows a path that is not orbital, and therefore can be achieved using a much simpler mechanism. In addition, the front end of the spindle can be moved in a neutral path or, alternatively, in an oblique path that plunges into the workpiece.
In another aspect, the present invention provides a method of reciprocating a spindle of a reciprocating saw, the spindle having a first cutting direction and a second cutting direction opposite the first cutting direction. The method comprises the steps of moving the front end along a first cutting path during the cutting stroke, the first cutting path characterized by movement at least partially in the first cutting direction, returning the front end along a return stroke (e.g., along the first cutting path), and adjusting the saw such that the front end moves along a second cutting path during the cutting stroke, the second cutting path characterized by movement at least partially in the second cutting direction. Preferably, the saw can also be adjusted such that the front end moves along a neutral cutting path during the cutting stroke, the neutral cutting path characterized by movement substantially perpendicular to the first and second cutting directions. By virtue of this method, the saw can be used to achieve a plunge cut in either down-cutting or up-cutting situations.